During manual breaths using neonatal SIBs, the delivered O2 concentration of nearly 40% is attained at clinically used inflation pressures and rates by using lower flows. A graded increase in O2 delivery from 40 to 99% was obtained with flow varying from 0.2 to 5 L/min and addition of reservoir. However, even at such low flows, reduction in O2 concentration below 40% was unattained.